The present invention relates to transfer pad printing systems and, in particular, to a method and apparatus for loading sealed paint pods 32 or pods on such systems.
Referring to FIG. 1, a transfer pad printing system 10 provides a clichxc3xa9 12 having a flat and polished upper surface 14. Shallow paint channels 16 cut or etched into the upper surface of the clichxc3xa9 12 define a pattern to be printed. The clichxc3xa9 12 is ferromagnetic, meaning that it is attracted to magnets but not necessarily magnetic, and may be a stainless steel plate or similar material.
During printing, the shallow paint channels 16 are filled with paint. Any extra paint on the upper surface 14 of the clichxc3xa9 12 is then scraped off or xe2x80x9cdoctoredxe2x80x9d. A transfer pad 20 composed of an elastomer such as silicone rubber is then positioned over the paint channels 16 as indicated by arrow 22 and pressed downward against the paint channels 16 where it deforms and accepts paint from the paint channels 16.
The transfer pad 20 is then lifted away from the clichxc3xa9 12, as indicated by arrow 24, and moved to another station (not shown), where it may be pressed against a registered part to be printed (not shown), transferring to that part, the image defined by the paint channels 16.
Transfer pad printing can be extremely precise but normally requires that the clichxc3xa9 12 and part be precisely registered with respect to movement of the transfer pad 20. In this regard, the clichxc3xa9 12 is tightly clamped by clamping structure 28 which provide vernier adjustments 30 allowing for precise registration of the clichxc3xa9 12 with the remote part and transfer pad 20.
Referring to FIGS. 1 and 2, filling the paint channels 16 in the clichxc3xa9 12 may be done with a sealed paint cup or xe2x80x9cpaint podxe2x80x9d 32. The paint pod 32 provides a cylindrical cup having a doctoring edge 34 surrounding an opening 36 of the cup. The doctoring edge is sharpened to terminate precisely at a plane. Centered within the paint pod 32 and attached thereto is a magnet 38 having one pole face offset slightly below the doctoring edge 34.
In use, the paint pod 32 is filled with paint 40 then attached to the clichxc3xa9 12. For this purpose, the clichxc3xa9 12 is inverted so that upper surface 14 of the clichxc3xa9 12 faces downward to cover the opening 36 of the paint pod 32. The magnet 38 pulls the upper surface 14 of the clichxc3xa9 12 against the doctoring edge 34 of the paint pod 32 which together form a seal preventing leakage of the paint 40. The connected paint pod 32 and clichxc3xa9 12 are then inverted putting the upper surface 14 on the upper side.
The clichxc3xa9 12 is then placed within the clamping structure 28 and registered with the rest of the transfer pad printing system 10.
A pivot arm 42 is then attached to base 44 of the paint pod 32. During operation of the transfer pad printing system 10, the pivot arm 42 slides the paint pod 32 across the clichxc3xa9 12 as indicated by arrow 46 in between pressings of the pad 20 against the paint channels 16. When the paint pod 32 is over the paint channels 16, it fills the paint channels 16 with paint 40. As the paint pod 32 is withdrawn, the doctoring edge 34 removes the paint from the remainder of the upper surface 14.
The sealing of the paint pod 32 against the upper surface 14 of the clichxc3xa9 12 prevents evaporation of the solvent of the paint 40 during long press runs. For such long press runs, however, the amount of paint held within the paint pod 32 may be insufficient and it may be necessary to refill the paint pod 32 a number of times. This refilling process can be quite costly in terms of lost production. A particular problem is the removal of the clichxc3xa9 12 and registering it again when the clichxc3xa9 12 is replaced within the clamping structure 28. Precise registration is time consuming and may require test impressions to assure that the registration is correct.
The present invention provides a method and apparatus for refilling paint pods without disturbing the clichxc3xa9. By preserving the registration of the clichxc3xa9, time-consuming re-registration of the clichxc3xa9 is eliminated.
The invention provides a loader plate that covers the pod during transfer operations. The surface of the loader plate is precisely ground and the loader plate is fitted with alignment arms so that it may attached to the clichxc3xa9 and the paint pod may be slid between the two without leakage of paint. Extra loader plates and paint pods allow the paint pods to be preloaded, eliminating refill time as well.
More specifically, the present invention provides a loading platform for paint pods comprising a loader plate having an upper surface sized to receive and cover a dispensing opening in the paint pod. Alignment arms attached to the loader plate engage a clichxc3xa9 and align a transfer edge of the loader plate into gapless abutment with an edge of the clichxc3xa9 so that the upper surface of the loader plate is substantially coplanar with an upper surface of the clichxc3xa9. The arms flank a transfer region along the transfer edge of the loader plate sufficient in width to allow continuous sliding passage of the paint pod along the upper surface of the loader plate across the transfer region to the upper surface of the clichxc3xa9.
It is thus one object of the invention to provide a simplified means of loading paint pods without removal of the clichxc3xa9.
The alignment arms may extend in cantilevered fashion over the transfer edge from the upper surface of the loader plate.
It is an object of the invention to provide an alignment system that is easily viewed by the operator and that works with a wide variety of clichxc3xa9s, all of which can be certain to have an upper planar surface.
The cantilevered portion of the transfer arms may have a lower planar surface coplanar with the upper surface of the loader plate, and the upper surface of the clichxc3xa9 when engaged with the clichxc3xa9.
It is thus another object of the invention to provide a simple mechanism for ensuring alignment of the upper surface of the clichxc3xa9 and loader plates.
The transfer arms may have embedded magnets on their cantilevered portions at the lower planar surface so that the magnets attract the clichxc3xa9 when the alignment arms are engaged with the clichxc3xa9.
It is another object of the invention to simplify the loading process by assisting the operator in holding the loader plate against the clichxc3xa9. The cantilevered arms convert out of plane tipping of the loader plate into vertical disengagement of the magnets, a mode in which they have great strength.
The alignment arms may be non-ferromagnetic.
It is thus another object of the invention to eliminate distortions in the magnet fields such as may reduce their attractive power.
The loader plate may be ferromagnetic.
Another object of the invention is to provide a loader plate that attracts the magnet of the paint pod preventing slippage or premature release of paint.
The plate may include an upwardly extending fence structure preventing continuous sliding passage of the paint pod along the upper surface of the loader plate, off the loader plate, except across the transfer region.
Thus, it is another object of the invention to eliminate possible paint leakage caused by sliding of the paint pod in directions other than onto the clichxc3xa9.
The transfer edge of the loader plate may further include magnets providing in-plane attraction of the loader plate to the clichxc3xa9.
Thus, it is another object of the invention to provide a force holding the clichxc3xa9 and loader plate together that supplements the magnets in the attachment arms, which provide lesser sliding resistance.
The loader plate upper surface provides a surface finish and flatness so that the paint pod, when loaded with paint, may be slid along the upper surface without substantial loss of paint.
Thus, it is another object of the invention to generally match the surface flatness and finish of the clichxc3xa9.
The transfer edge may include at least one pocket for accepting a projection of clichxc3xa9 retaining structure when the clichxc3xa9 is held in the retaining structure facilitating engagement of the loader plate and clichxc3xa9.
Thus, it is another object of the invention to accommodate a clamping structure holding the clichxc3xa9 without removal of that clamping structure which might affect registration.
These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention.